Respiration rate control system

ABSTRACT

A system for timing the maximum lengths of inspiration and expiration phases of the respiration cycles of a positive pressure breathing apparatus, the rate control system including a timing cylinder with a movable piston therein forming two mutually adjustable timing chambers, two conduits receiving equal flows of gas through an adjustable needle valve and operable alternately to charge the respective chambers, and pressureresponsive actuators pressurized through the respective chambers and each operable upon attainment of a selected actuating pressure level in the associated chamber to produce a pressure signal for terminating one phase and initiating the next. The chambers are activated alternately by a controller which vents one chamber while sealing the other.

United States Patent 11 1 Weigl 1 1 RESPIRATlON RATE CONTROL SYSTEM [75] Inventor:

[73] Assignee: Puritan-Bennett Corporation,

Kansas City, Mo.

22 Filed: Dec. 11,1972

211 App]. No.: 313.984

James Weigl, Santa Monica, Calif.

[52] US. Cl 128/145.8; 137/624.14 [51] Int. Cl A6lm 16/00 [58] Field of Search 128/1458, 145.6, 145.5,

[ 1 June 17, '1975 Primary ExaminerRichard A. Gaudet Assistant Examiner-Henry J. Recla Attorney, Agent, or FirmFulwider, Patton. Rieber, Lee & Utecht [57] ABSTRACT A system for timing the maximum lengths of inspiration and expiration phases of the respiration cycles of a positive pressure breathing apparatus, the rate control system including a timing cylinder with a movable piston therein forming two mutually adjustable timing chambers, two conduits receiving equal flows of gas through an adjustable needle valve and operable alternately to charge the respective chambers, and pressure-responsive actuators pressurized through the respective chambers and each operable upon attainment of a selected actuating pressure level in the associated chamber to produce a pressure signal for terminating one phase and initiating .the next. The chambers are activated alternately by a controller which vents one chamber while sealing the other.

19 Claims, 1 Drawing Figure RESPIRATION RATE CONTROL SYSTEM BACKGROUND OF THE INVENTION This invention relates to a respiration rate control system. and has particular reference to an improved system for controlling the maximum time intervals of the inspiration and expiration phases of a respiration apparatus for administering intermittent positive pressure breathing (IPPB) therapy to a patient.

Conventional respiration units for administering IPPB therapy may be patient-controlled. that is. cycled in response to spontaneous breathing efforts by a patient who is breathing at a self-controlled rate. In such a unit (cg. a unit of the type disclosed in US. Pat. No. 3,362,404). a slight inspiratory effort by the patient produces a pressure drop at the delivery means, typically a face mask. and the unit is activated by this pressure drop to begin delivering gas under pressure to the patient through the delivery means. thus initiating an inspiration phase. The gas typically is oxygen or a mixture of oxygen and air. sometimes supplied with vaporiZed or nebulizcd medication.

As the patient's lungs are inflated, the flow rate to the patient is reduced until a selected terminal flow rate is achieved. at which point the supply of gas is terminated to terminate the inspiration phase. and the patient is permitted to exhale through the face mask. during an expiration phase. This phase is terminated in response to the next normal inspiratory effort by the patient, which initiates the next inspiration phase. Accordingly, the respiration unit may alternately supply gas under pressure and allow the patient to exhale, solely under the control ofthe patient and at a rate controlled by his own natural breathing rhythm.

When the condition of a patient is such that his own respiratory efforts are feeble. or so slow as to be insufficient to produce a satisfactory breathing rate, automatic cycling devices have been provided to actuate the respiration apparatus at a selected and often adjust able. rate. If the patient is incapable of proper breathing. the breathing cycle may be controlled solely by such a cycling device, whereas the cycling device otherwise may serve simply as a guarantor of maximum time intervals for inspiration and expiration. In addition to adjusting the rate to produce different numbers of cycles per minute. it often is desirable to be able to adjust the relative lengths of the inspiration and expiration phases within each cycle.

Automatic cycling devices have been available prior to the present invention, one example being the mechanical/pneumatic attachment shown in US. Pat. No. 2.867.210. in which the cycling is controlled by the expansion and contraction of a bellows, at adjustable rates which determine the maximum times of the inspiration and expiration phases. The movements of the bellows in this attachment are applied to an actuating lever which controls the cycling valve of the IPPB apparatus. Illustrative of another. more complex approach is the electronically controlled apparatus dis closed in L'.S. Pat. No. 3.191595.

While these and other cycle-timing systems have been capable of accomplishing their intended functions. the need has existed for an improved system characterized by accuracy and versatility in adjustment. reliability. and simplicity in construction and operation.

SUMMARY OF THE INVENTION The present invention resides in an improved respiration rate control system of the foregoing general character which is readily adjustable to provide a wide range of available cycle times, and also is adjustable to vary the ratio of inspiration to expiration time within each cycle, with a relatively high degree of accuracy, and in which each of these adjustments can be made without disturbing the other. That is. the cycle rate can be changed without changing the ratio, and the ratio can be changed without changing the rate. Moreover, the system is relatively simple in construction and reliable in operation, and can be operated by pressurized gas that is readily available in the associated respiration apparatus.

More specifically, and as illustrated schematically herein as the preferred embodiment of the invention, the improved system has two timing chambers of preselected volumes which determine the ratio of the inspiration and expiration phases, and means for charging the respective chambers, alternately during the associated respiration phases, with fluid under pressure delivered to each chamber at a preselected rate. to raise the chamber pressure to a selected actuating pressure in a time interval determined by the volume of the chamber. When this pressure level is attained, pressureactuated phase control means terminate the timed phase and initiate the next phase, which is timed in the same manner as the other chamber is charged to the selected actuating-pressure level.

Adjustment of the cycle rate is accomplished by varying the charging rate for the two chambers, preferably with a simple needle valve for varying a common feed flow that is divided equally between the two chambers. Adjustment of the volumetric ratio of the timing chambers, to vary the relative phase times within a cycle of selected total length, is accomplished by moving a common wall of the two chambers, whereby any change in one volume is accompanied by an equal but opposite change in the other volume.

The presently preferred pressure-actuated phase control means includes an actuating member movable back and forth between timing and actuating positions, and an inflatable actuator receiving fluid under pressure from the associated timing chamber and operable as it is inflated to urge the member toward the actuating position. The member is held in the timing position, for example, by a magnet, until the force developed by the inflatable actuator attains a selected level, and then is momentarily shifted to the actuating position. This movement is used to terminate one phase and to initiate the next.

The preferred charging means directs two metered charging flows toward the respective chambers, and a controller actuated by gas supplied during inspiration alternately vents one timing chamber while sealing the other, to activate the appropriate chamber during each phase. Thus, the controller activates the appropriate chamber in response to initiation and cessation of inspiration, and the phase-control means terminates each phase in response to the attainment of the selected actuating pressure in the active chamber.

Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING The single FIGURE of the drawing is a schematic view, partly in cross-section, of a respiration apparatus equipped with a rate control system embodying the novel features of the present invention.

DETAILED DESCRIPTION As shown in the drawing for purposes of illustration, the invention is embodied in a rate control system, indicated generally by the reference number in the right portion of the drawing, for controlling the maximum intervals of the inspiration and expiration phases of an IPPB respiration apparatus 11, the main components of which are illustrated schematically on the left portion of the drawing. The rate control system may be provided as a separate attachment for the basic respiration apparatus, or may be built into the apparatus as an integral part thereof.

The rate control system 10 may be used with various types of respiration apparatus, the apparatus 11 being merely illustrative of one type in which gas from a source 12 is delivered through a conduit to control valve means 13 that is actuated between open (inspiration) and closed (expiration) conditions by two pilotoperated valves 14 and 15. Actuating signals are applied to these two valves through conduits l7 and 18, respectively, to shift them selectively from the off conditions indicated by the arrows l9 and 20, to the on" conditions indicated by the arrows 21 and 22.

When both pilot valves are off, the control valve means 13 is in complete control of delivered flow. When the inspiration start valve 14 is momentarily on, a connecting conduit 23 between the pilot valves is vented through a port 24, and communicates through the pilot valve with a conduit 25 leading to the control valve means, and the ambient pressure thus applied actuates the control valve means to an open condition, passing primary gas from the source 12 to a main flow conduit 27. As soon as the pilot valve 14 is returned to the off position, control of delivered flow is returned to the flow responsive control means 13.

Through the conduit 27, the gas flows to a regulator 28 for controlling the flow rate in accordance with the back pressure in the apparatus, and from the regulator, the gas flows through a conduit 29 to delivery means 30, and thus to the patient. The regulator reduces the flow rate as the lungs of the patient become inflated, and also can be used to dilute the primary gas flow with outside air.

Inspiration can be terminated and expiration initiated by applying a momentary signal to the pilot valve 14 through the conduit 17 to momentarily switch this valve to the on condition, in which gas at regulated input pressure from a conduit 32 constantly communicating with the source 12 through the control valve means, is delivered to the conduit 25. This pressure signal shifts the control valve means to the closed condition to terminate the flow to the main conduits 27 and 29. When pilot valve 15 returns to the off condition, control of delivered flow is again returned to the flow responsive control means 13.

The patient is permitted to exhale through an exhalation port 33 adjacent the delivery means 30, this port being closed during inspiration by an inflatable closure 34 that is pressurized, during inspiration, through a conduit 35 connected to the main conduit 27 and having a flow restrictor 37 therein. During expiration, the pressure in the inflatable closure is relieved through a restricted vent 38, thus permitting the patient to exhale through the port 33.

For patient-controlled cycling, a patient-actuated control 39 is connected by a conduit 40 to the main conduit 29 adjacent the delivery means 30, to sense an inspiratory effort by the patient and produce a momentary pressure signal which is applied through a conduit 41, and a one-way check valve 42 therein, to the signal conduit 17 of the inspiration start valve 14. This causes the control valve means to open, and begin delivering gas to the patient through the main conduits 27 and 29. Pressure in the conduit 27 is applied through the conduit 35 to the closure 34 to seal the exhalation port 33, and also, through another conduit 37, to another pilot valve 43 to switch it from the off condition to the on condition, indicated by the arrows 44 and 45, respectively.

When off (during expiration), this valve supplies actuating pressure from the pressurized line 32 to the patient-actuated contol 39 through two conduits 47 and 48. When on (during inspiration), the valve 45 switches the actuating pressure to a conduit 49 that may have a branch 50 leading to a nebulizer (not shown) for adding medication to the gas, the conduit 49 leading also to the rate control system 10.

Termination of inspiration may be accomplished in response to dropping of the flow rate to a sensed terminal level, by the control valve means, the flow rate being reduced by the regulator 28 in response to the back-pressure build-up in the system and thus being indicative of the degree of inflation of the patients lungs. When this occurs, the closing of the control valve means relieves the pressure in the main conduits 27 and 29, permitting the exhalation port 33 to be opened and also removing the signal from the pilot valve 43 to switch it to the off condition.

One flow responsive control valve arrangement of the foregoing type is shown in the aforesaid US. Pat. No. 3,362,404, and others are available. A regulator suitable for use in the illustrative system is that sold by Puritan-Bennett Corporation, Santa Monica, Calif., as the 0666 Diluter Regulator. The three pilot valves l4, l5 and 43 may be simple switching valves of the diaphragm type, the details of which are well within the skill of the art.

In accordance with the present invention, the rate control system 10 controls the maximum lengths of the inspiration and expiration phases during successive cycles, and also sets the cycling rate, while permitting the accurate and independent adjustment of both the cycling rate and the ratio of phase timing in a rapid and simple manner. To these ends, the rate control system has two timing chambers 51 and 52 of mutually variable volumes, means for charging the chambers alternatively during the alternating phases with gas at a preselected rate to raise the pressure in each chamber progressively toward a preselected actuating level, and means responsive to attainment of that level in each chamber when it is active, to terminate one phase and initiate the other.

Accordingly, the relative volumes of the timing chambers 51 and 52 determine the proportion of each cycle devoted to each of the phases, and the ratio of the phase times, while the charging rate determines the cycling rate. The combined volume of the two chambers remains constant, so variations in ratio do not affect the rate, nor do variations in rate affect the ratio. The result is a versatile, easily adjusted, and relatively simple and reliable rate control system.

More specifically, the timing chambers 51 and 52 herein are the opposite end portions of a timing cylinder 53, and are separated by a piston 54 forming a common movable wall of the two chambers, the piston hav' ing a peripheral O-ring 55 for sealing the chambers from each other and a pair of oppositely extending piston rods 56:: and 56b sealed relative to the cylinder by O-rings 59a and 59b. The piston is adjustably positioned in the cylinder by a screw mechanism at one end of the cylinder, herein illustrated an internally threaded, coaxial sleeve 57 on one end of the cylinder, and an externally threaded end portion 58 of the rod An adjusting knob 60 is mounted on the outer end of the rod end 58. and suitable calibrations (not shown) may be provided to indicate the phase ratio to be obtained in various adjusted positions of the rod. A normal inspiration/expiration ratio is l:l-/2 and a suitable adjustment range is from lzl to 1:4.

To charge the timing chambers 51 and 52 at a selected rate. two charging conduits 61 and 62 open into the respective chambers adjacent the ends thereof, and are connected through calibrated orifices 63 and 64 to a supply conduit 65 leading to the constantly pressur ized conduit 32, and thus constantly receiving a flow of gas under regulated input pressure. An adjustable needle valve 67 controls the rate of flow to the two charging conduits 61 and 62, and this flow is divided by the two orifices 63 and 64 into two charging flows of equal rates in the charging conduits. The needle valve 67 also may be calibrated to indicate the rate produced in different adjusted positions of the valve. typically from ten to sixty cycles per minute.

With this arrangement, equal charging flows are directed continuously toward the two chambers 51 and 52 while the apparatus is in operation. To activate the chambers alternately during the alternating inspiration and expiration phases, a controller 68 is provided to alternately vent one chamber while sealing the other, thereby inactivating one charging conduit and associated chamber while activating the other. Basically, this controller comprises two venting orifices 69 and 70 communicating with the respective charging conduits 61 and 62, respectively, and a blocking lever 71 swingable between two blocking positions, against the respective orifices, by means of inflatable actuators 72 and 73 on opposite sides of the lever. The actuator 72 is inflated during inspiration to hold the lever against the orifice 70 to seal inspiration timing chamber 52, and the actuator 73 is momentarily inflated when inspiration is to he ended to hold the lever against the orifice 69 to seal the expiration timing chamber 51. A light spring 74 assists the actuator 73, and will hold the lever against the orifice 69 when both actuators are deflated or inflated.

Inflation of the expiration-timing actuator 73 is effected through a conduit 75 shown as extending downwardly to a pressure divider formed by two restrictors 77 and 78, pressure being applied through the restrictor 78 from a conduit 79 connected to a supply conduit 80 communicating with the conduit 65 ahead of the needle valve 67. The phase-control means include a bleed orifice 81 which, when blocked. applies the output pressure of the pressure divider to the actuator 73, and when unblocked, vents the actuator.

Inflation of the inspiration timing actuator 72 is effected through the conduit 49 which receives pressurized gas from the pilot valve 43 whenever the respiration apparatus 11 is in the inspiration phase. This gas is delivered to the actuator 72 through a one-way check valve 82 at the beginning of each inspiration phase, and holds the lever 71 in blocking engagement with the orifice and an adjacent second orifice 87, as long as in spiration continues. Upon termination of inspiration, however, the pressure supply in the conduit 49 is terminated, but pressure is maintained through a branch conduit 83 coupled to a restricted bleed passage 84 and to a conduit 85 terminating in the orifice 87. This has the effect of holding the lever 71 to block the orifice 70 until such time as the actuator 73 is pressurized through the conduit 75, thus maintaining a constant breathing cycle rate even if the delivered flow is stopped by the flow responsive control valve before the allotted inspiration time has completely elapsed.

The presently preferred phase-control means include two conduits 88 and 89 leading from the respective timing chambers 51 and 52 to two pressure-responsive actuators 90 and 91, which also may be inflatable mem bers as shown in the drawing. Each of these actuators thus is inflated with the same pressure that is developed in the associated chamber, and may take the form of hollow mushroom 0r balloon" members having movable walls of freely flexible plastic or rubber.

Above each actuator 90, 91 is a blocking lever 92, 93 which is releasably held with a selected force in a lowered, timing position, and is movable upwardly by the associated actuator to a raised, actuating position against a bleed orifice, one of these orifices being the one 81 previously referred to and the other being numbered 94 in the drawing. The pressure signals produced by blocking these bleed orifices are the actuating signals for terminating the respective phases.

In this instance, the holding force is applied to each lever by a magnet 95, against which the lever is urged by a light spring 97, so that the lever will remain in the timing position until the force moment applied by the inflatable actuator exceeds the opposing, combined force moments of the spring and the magnet. When this occurs, the lever is shifted upwardly with a snap action into the blocking position.

As has been stated, blocking of the orifice 81 inflates the actuator 73 of the controller 68 to shift the lever 71 into engagement with the orifice 69, and thus begins timing of the expiration phase. At the same time, a back-pressure signal pulse is applied through a continuation 75a of the conduit 75 to the pilot valve 15 to shift it to the on condition, thereby applying the shut-off signal to the control valve means.

Similarly, blocking of the orifice 94 by the lever 92 after the timing of an expiration phase creates a backpressure signal pulse in a conduit 98 which leads, through a one-way check valve 99, to the signal conduit 17 of the other pilot valve 14. This shifts this pilot valve to the on condition, in which ambient pressure is applied through the pilot valve 15 to the control valve means to open the latter and start inspiration, just as does the signal produced by the patient-actuated control 39 in response to a sensed inspiratory effort of the patient. In each case, the response of the controller 68 to change the phases, also vents the previously active timing chamber, returning to the starting pressure level (herein ambient pressure) and also vents the associated actuator 90, 91. Accordingly, the blocking lever 92, 93 is returned to its timing position.

With the foregoing arrangement, the rate control system 10 is cycled repeatedly between its two conditions, and remains operable to terminate a phase if, at the end of the timing interval, the patient-actuated control 39 has not been actuated to do so. Of course, if the patients normal breathing function is completely incapacitated, the rate control system will provide complete control of the breathing cycles, as if the patientactuated control did not exist.

From the foregoing, it will be evident that the present invention enables the operator to adjust the rate control system 10 in an extremely simple manner to vary both rate and ratio within the ranges of adjustment provided, respectively, by the needle valve 67 and the volume-adjusting knob 60. Moreover, neither of these two adjustments requires compensating or balancing adjustments in the other, since they both are independent and the rate and ratio are automatically correlated by the mutually adjustable timing chambers 51 and 52.

It also will be evident that, while one embodiment has been illustrated and described, in connection with a general illustration of one type of respiration apparatus, the system may be readily adapted to different types of respiration apparatus, and various modifications and changes may be made in the system without departing from the spirit and scope of the invention.

I claim:

1. For use with a respiration apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, and comprising:

a hollow enclosure of regular cross-sectional shape having a movable wall dividing the interior of the enclosure into first and second timing chambers of mutually adjustable volumes;

means for variably positioning said wall within said enclosure to vary the ratio of the volumes of said chambers while maintaining a constant total volume;

means for supplying charging gas at the same preselected rate alternately to said chambers and raising the pressure therein from a preselected starting pressure level to a preselected actuating pressure level, whereby the time required to attain said actuating pressure level varies in accordance with the ratio of said volumes and the ratio of said volumes determines the ratio of inspiration time to expiration time;

means for selectively varying said preselected rate to adjust the cycle rate of said system independently of the ratio of inspiration time to expiration time;

and phase control means operable in response to attainment of said actuating pressure level in said first and second chambers to produce first and second signals, respectively, for terminating one phase of the respiration cycle and initiating the other phase thereof.

2. A rate control system as defined in claim 1 in which said enclosure is a cylinder and said wall is a piston slidably positioned therein.

3. A rate control system as defined in claim 2 in which said means for variably positioning said piston include a piston rod and a screw mechanism acting through said rod to slide said piston within said cylinder.

4. A rate control system as defined in claim 1 in which said means for supplying charging gas include a first conduit for receiving a supply flow of gas at regulated pressure, two charging conduits leading from said first conduit to said chambers, and means for dividing the supply flow into two equal charging flows.

5. A rate control system as defined in claim 4 in which said means for selectively varying said preselected rate comprises a calibrated needle valve controlling flow through said first conduit.

6. A rate control system as defined in claim 4 further including a controller for venting each of said chambers while sealing the other, thereby alternately activating said chambers, and means for actuating said controller in response to initiation of the respected phases of respiration.

7. A rate control system as defined in claim 1 in which said phase control means comprise pressureresponsive actuators receiving pressure from said chambers and operable upon attainment of said actuating pressure levels therein.

8. For use with a respiration apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, and comprising:

means defining first and second timing chambers of preselected volumes, said volumes having a preselected ratio;

means operable during each inspiration phase to charge said first chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level;

first phase-control means responsive to attainment of a preselected actuating pressure level in said first chamber to terminate the inspiration phase and initiate an expiration phase;

means operable during each expiration to change said second chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level;

and second phase-control means responsive to attainment of a selected actuating pressure level in said second chamber to terminate the expiration phase and initiate an inspiration phase, whereby said phases are timed in accordance with said charging rates and volumes to produce breathing cycles of selected length with each phase consituting a preselected portion of said length;

and in which said charging means for said chambers comprise a common source of gas under pressure producing a single regulated flow of gas, means dividing said regulated flow into two equal flows and directing such flows through first and second conduits to the respective chambers, and said first and second phase-control means include a controller operable during the inspiration phase to vent said second chamber while sealing said first chamber, and during said expiration phase to vent said first chamber while sealing said second chamber, said controller being actuated cyclically in response to the attainment of said preselected pressure levels in said chambers, and said controller including first and second vent orifices for venting said first and second conduits, respectively, a blocking member movable between two blocking positions over the respective orifices and operable in each blocking position to effect charging of the associated chamber through the associated conduit, and means operated by said first and second phase-control means to position said blocking member over one of said orifices to vent said second chamber during said inspiration phase and to vent said second chamber during said expiration phase.

9. A rate control system as defined in claim 8 in which said means for positioning said blocking member comprise a spring urging said blocking member toward one of said orifices, first and second inflatable actuators arranged on opposite sides of said member to urge the latter toward the first and second orifices respectively, when inflated, a source of fluid under pressure for each inflatable actuator, and means for applying the fluid under pressure to the respective inflatable actuators in response to attainment of preselected actuating pressure in the respective timing chambers.

10. For use with a respiration apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, and comprising:

means defining first and second timing chambers of preselected volumes, said volumes having a preselected ratio;

means operable during each inspiration phase to charge said first chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level;

first phase-control means responsive to attainment of a preselected actuating pressure level in said first chamber to terminate the inspiration phase and initiate an expiration phase; means operable during each expiration to charge said second chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level;

second phase-control means responsive to attainment of a selected actuating pressure level in said second chamber to terminate the expiration phase and initiate an inspiration phase, whereby said phases are timed in accordance with said charging rates and volumes to produce breathing cycles of selected length with each phase constituting a preselected portion of said length;

means for selectively adjusting said rates, thereby to vary the charging times for said first and second timing chambers together and the total time of each breathing cycle;

and means for selectively adjusting the volume of each of said chambers, thereby to vary the charging times of said chambers with selected flow rates, and for maintaining the combined volumes of said chambers constant by increasing one volume in direct relation to any decrease in the other, thereby maintaining the total cycle time constant while varying the proportions thereof for the respective phases.

11. A rate control system as defined in claim 10 in which said flow-rate adjusting means comprises a needle valve through which fluid flows to both of said chambers.

12. A rate control system as defined in claim 10 in which each of said first and second phase-control means comprises a member movable between a timing position and an actuating position, means normally holding said member in said timing position, and means responsive to the pressure level in the associated chamber and operable when such pressure level attains said actuating pressure level to move said member to said actuating position.

13. A rate control system as defined in claim 12 in which said pressure-responsive actuating means include inflatable members receiving fluid under pressure from the respective chambers and urging the levers toward the actuating positions to move them to such positions when the force moment of inflation exceeds the holding force moment.

14. A rate control system as defined in claim 13 in which each of said holding means include a magnet exerting a preselected holding force on said lever, and operable to release said lever with a snap action when the force moment of the associated inflatable member exceeds said holding force moment.

15. A rate control system as defined in claim 10 in which said charging means for said chambers comprise a common source of gas under pressure producing a single regulated flow of gas, means dividing said regulated flow into two equal flows and directing such flows through first and second conduits to the respective chambers, and said first and second phase-control means include a controller operable during the inspiration phase to vent said second chamber while sealing said first chamber, and during said expiration phase to vent said first chamber while sealing said second chamber, said controller being actuated cyclically in response to the attainment of said preselected pressure levels in said chambers.

16. For use with a respiration apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, and comprising:

means defining first and second timing chambers of preselected volumes, said volumes having a preselected ratio and said chambers having a common movable wall;

means operable during each inspiration phase to charge said first chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level;

first phase-control means responsive to attainment of a preselected actuating pressure level in said first chamber to terminate the inspiration phase and initiate an expiration phase; means operable during each expiration to charge said second chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level;

second phase-control means responsive to attainment of a selected actuating pressure level in said second chamber to terminate the expiration phase and initiate an inspiration phase, whereby said phases are timed in accordance with said charging rates and volumes to produce breathing cycles of selected length with each phase constituting a preselected portion of said length;

and means connected with said movable wall to move the same back and forth within said chambers, for selectively adjusting the volume of each of said chambers, thereby to vary the charging times for said chambers with selected flow rates.

17. For use with a respiration apparatus for deliver ing gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase. and comprising:

means defining first and second timing chambers or preselected volumes, said volumes having a preselected ratio;

means operable during each inspiration phase to charge said first chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level;

first phase-control means responsive to attainment of a preselected actuating pressure level in said first chamber to terminate the inspiration phase and initiate an expiration phase; means operable during each expiration to charge said second chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level;

and second phase-control means responsive to attainment of a selected actuating pressure level in said second chamber to terminate the expiration phase and initiate an inspiration phase, whereby said phases are timed in accordance with said charging rates and volumes to produce breathing cycles of selected length with each phase constituting a preselected portion of said length;

and in which each of said first and second phasecontrol means comprises a lever movable between a timing position and an actuating position, means normally holding said lever in said timing position, means responsive to the pressure level in the associated chamber and operable when said pressure level attains said actuating pressure level to move said lever to said actuating position, and a bleed orifice spaced from said lever in said timing position and blocked by said lever in said actuating position.

18. For use with a respirator apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, said 12 system comprising:

timing chamber means of preselected volume for timing each breathing cycle;

means for charging said timing chamber means to a preselected pressure level with fluid entering at a preselected flow rate, thereby to time each breathing cycle;

a single rate control means for selectively adjusting the flow rate to vary the breathing cycle time independently of the ratio of inspiration time to expiration time;

pressureactuated means coupled with said timing chamber means, for terminating the inspiration phase and initiating the expiration phase, and thereby dividing the breathing cycle time in a preselected ratio of inspiration time to expiration time; and a single ratio control means for selectively varying the ratio of inspiration time to expiration time independently of the breathing cycle time.

19. For use with a respirator apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, said system comprising:

timing chamber means of preselected volume for timing each breathing cycle, said timing chamber means including first and second chambers;

means for charging to a preselected pressure level said first chamber during the inspiration phase, and said second chamber during the expiration phase, with fluid entering at a preselected flow rate, thereby to time each breathing cycle;

a single rate control means for selectively adjusting the flow rate to vary the breathing cycle time;

pressure-actuated means coupled with said timing chamber means, for terminating the inspiration phase and initiating the expiration phase, and thereby dividing the breathing cycle time in a preselected ratio of inspiration time to expiration time; and

a single ratio control means for selectively varying the ratio ofinspiration time to expiration time independently of the breathing cycle time, said ratio control means including a movable piston separating said first and second chambers, whereby movement of said piston changes the ratio of inspiration time to expiration time independently of the breathing cycle time, by varying the ratio of the volumes of said first and second chambers independently of their total volume.

UNITED STATES PATENT OFFICE (IERTIFECATE 0F CORRECTION PATENT NO. 1 3,889,669

DATED :June 17, 1975 rrrvmrorusy JAMES WEIGL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 8, Column 8, line 44, "change" should be charge line 54, "consituting" should be --constituting-.

Claim 1?, Column ll, line 15, "or" should be of Signed and Sealed this sixteenth D Ely Of September 1 975 [SEAL] A ttest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (ommr'sximrer oflatents and Trademarks 

1. For use with a respiration apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, and comprising: a hollow enclosure of regular cross-secTional shape having a movable wall dividing the interior of the enclosure into first and second timing chambers of mutually adjustable volumes; means for variably positioning said wall within said enclosure to vary the ratio of the volumes of said chambers while maintaining a constant total volume; means for supplying charging gas at the same preselected rate alternately to said chambers and raising the pressure therein from a preselected starting pressure level to a preselected actuating pressure level, whereby the time required to attain said actuating pressure level varies in accordance with the ratio of said volumes and the ratio of said volumes determines the ratio of inspiration time to expiration time; means for selectively varying said preselected rate to adjust the cycle rate of said system independently of the ratio of inspiration time to expiration time; and phase control means operable in response to attainment of said actuating pressure level in said first and second chambers to produce first and second signals, respectively, for terminating one phase of the respiration cycle and initiating the other phase thereof.
 2. A rate control system as defined in claim 1 in which said enclosure is a cylinder and said wall is a piston slidably positioned therein.
 3. A rate control system as defined in claim 2 in which said means for variably positioning said piston include a piston rod and a screw mechanism acting through said rod to slide said piston within said cylinder.
 4. A rate control system as defined in claim 1 in which said means for supplying charging gas include a first conduit for receiving a supply flow of gas at regulated pressure, two charging conduits leading from said first conduit to said chambers, and means for dividing the supply flow into two equal charging flows.
 5. A rate control system as defined in claim 4 in which said means for selectively varying said preselected rate comprises a calibrated needle valve controlling flow through said first conduit.
 6. A rate control system as defined in claim 4 further including a controller for venting each of said chambers while sealing the other, thereby alternately activating said chambers, and means for actuating said controller in response to initiation of the respected phases of respiration.
 7. A rate control system as defined in claim 1 in which said phase control means comprise pressure-responsive actuators receiving pressure from said chambers and operable upon attainment of said actuating pressure levels therein.
 8. For use with a respiration apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, and comprising: means defining first and second timing chambers of preselected volumes, said volumes having a preselected ratio; means operable during each inspiration phase to charge said first chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level; first phase-control means responsive to attainment of a preselected actuating pressure level in said first chamber to terminate the inspiration phase and initiate an expiration phase; means operable during each expiration to change said second chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level; and second phase-control means responsive to attainment of a selected actuating pressure level in said second chamber to terminate the expiration phase and initiate an inspiration phase, whereby said phases are timed in accordance with said charging rates and volumes to produce breathing cycles of selected length with each phase consituting a preselected portion of said length; and in which said charging means for said chambers comprise a common source of gas undEr pressure producing a single regulated flow of gas, means dividing said regulated flow into two equal flows and directing such flows through first and second conduits to the respective chambers, and said first and second phase-control means include a controller operable during the inspiration phase to vent said second chamber while sealing said first chamber, and during said expiration phase to vent said first chamber while sealing said second chamber, said controller being actuated cyclically in response to the attainment of said preselected pressure levels in said chambers, and said controller including first and second vent orifices for venting said first and second conduits, respectively, a blocking member movable between two blocking positions over the respective orifices and operable in each blocking position to effect charging of the associated chamber through the associated conduit, and means operated by said first and second phase-control means to position said blocking member over one of said orifices to vent said second chamber during said inspiration phase and to vent said second chamber during said expiration phase.
 9. A rate control system as defined in claim 8 in which said means for positioning said blocking member comprise a spring urging said blocking member toward one of said orifices, first and second inflatable actuators arranged on opposite sides of said member to urge the latter toward the first and second orifices respectively, when inflated, a source of fluid under pressure for each inflatable actuator, and means for applying the fluid under pressure to the respective inflatable actuators in response to attainment of preselected actuating pressure in the respective timing chambers.
 10. For use with a respiration apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, and comprising: means defining first and second timing chambers of preselected volumes, said volumes having a preselected ratio; means operable during each inspiration phase to charge said first chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level; first phase-control means responsive to attainment of a preselected actuating pressure level in said first chamber to terminate the inspiration phase and initiate an expiration phase; means operable during each expiration to charge said second chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level; second phase-control means responsive to attainment of a selected actuating pressure level in said second chamber to terminate the expiration phase and initiate an inspiration phase, whereby said phases are timed in accordance with said charging rates and volumes to produce breathing cycles of selected length with each phase constituting a preselected portion of said length; means for selectively adjusting said rates, thereby to vary the charging times for said first and second timing chambers together and the total time of each breathing cycle; and means for selectively adjusting the volume of each of said chambers, thereby to vary the charging times of said chambers with selected flow rates, and for maintaining the combined volumes of said chambers constant by increasing one volume in direct relation to any decrease in the other, thereby maintaining the total cycle time constant while varying the proportions thereof for the respective phases.
 11. A rate control system as defined in claim 10 in which said flow-rate adjusting means comprises a needle valve through which fluid flows to both of said chambers.
 12. A rate control system as defined in claim 10 in which each of said first and second phase-control means comprises a member movable between a timing positiOn and an actuating position, means normally holding said member in said timing position, and means responsive to the pressure level in the associated chamber and operable when such pressure level attains said actuating pressure level to move said member to said actuating position.
 13. A rate control system as defined in claim 12 in which said pressure-responsive actuating means include inflatable members receiving fluid under pressure from the respective chambers and urging the levers toward the actuating positions to move them to such positions when the force moment of inflation exceeds the holding force moment.
 14. A rate control system as defined in claim 13 in which each of said holding means include a magnet exerting a preselected holding force on said lever, and operable to release said lever with a snap action when the force moment of the associated inflatable member exceeds said holding force moment.
 15. A rate control system as defined in claim 10 in which said charging means for said chambers comprise a common source of gas under pressure producing a single regulated flow of gas, means dividing said regulated flow into two equal flows and directing such flows through first and second conduits to the respective chambers, and said first and second phase-control means include a controller operable during the inspiration phase to vent said second chamber while sealing said first chamber, and during said expiration phase to vent said first chamber while sealing said second chamber, said controller being actuated cyclically in response to the attainment of said preselected pressure levels in said chambers.
 16. For use with a respiration apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, and comprising: means defining first and second timing chambers of preselected volumes, said volumes having a preselected ratio and said chambers having a common movable wall; means operable during each inspiration phase to charge said first chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level; first phase-control means responsive to attainment of a preselected actuating pressure level in said first chamber to terminate the inspiration phase and initiate an expiration phase; means operable during each expiration to charge said second chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level; second phase-control means responsive to attainment of a selected actuating pressure level in said second chamber to terminate the expiration phase and initiate an inspiration phase, whereby said phases are timed in accordance with said charging rates and volumes to produce breathing cycles of selected length with each phase constituting a preselected portion of said length; and means connected with said movable wall to move the same back and forth within said chambers, for selectively adjusting the volume of each of said chambers, thereby to vary the charging times for said chambers with selected flow rates.
 17. For use with a respiration apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, and comprising: means defining first and second timing chambers or preselected volumes, said volumes having a preselected ratio; means operable during each inspiration phase to charge said first chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level; first phase-control means responsive to attainment of a preselected actuating pressure level in said first Chamber to terminate the inspiration phase and initiate an expiration phase; means operable during each expiration to charge said second chamber with fluid at a preselected rate to raise the pressure level therein progressively from a selected starting pressure level; and second phase-control means responsive to attainment of a selected actuating pressure level in said second chamber to terminate the expiration phase and initiate an inspiration phase, whereby said phases are timed in accordance with said charging rates and volumes to produce breathing cycles of selected length with each phase constituting a preselected portion of said length; and in which each of said first and second phase-control means comprises a lever movable between a timing position and an actuating position, means normally holding said lever in said timing position, means responsive to the pressure level in the associated chamber and operable when said pressure level attains said actuating pressure level to move said lever to said actuating position, and a bleed orifice spaced from said lever in said timing position and blocked by said lever in said actuating position.
 18. For use with a respirator apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, said system comprising: timing chamber means of preselected volume for timing each breathing cycle; means for charging said timing chamber means to a preselected pressure level with fluid entering at a preselected flow rate, thereby to time each breathing cycle; a single rate control means for selectively adjusting the flow rate to vary the breathing cycle time independently of the ratio of inspiration time to expiration time; pressure-actuated means coupled with said timing chamber means, for terminating the inspiration phase and initiating the expiration phase, and thereby dividing the breathing cycle time in a preselected ratio of inspiration time to expiration time; and a single ratio control means for selectively varying the ratio of inspiration time to expiration time independently of the breathing cycle time.
 19. For use with a respirator apparatus for delivering gas from a source of gas under pressure cyclically to a patient through delivery means, a rate control system for timing successive breathing cycles each having an inspiration phase followed by an expiration phase, said system comprising: timing chamber means of preselected volume for timing each breathing cycle, said timing chamber means including first and second chambers; means for charging to a preselected pressure level said first chamber during the inspiration phase, and said second chamber during the expiration phase, with fluid entering at a preselected flow rate, thereby to time each breathing cycle; a single rate control means for selectively adjusting the flow rate to vary the breathing cycle time; pressure-actuated means coupled with said timing chamber means, for terminating the inspiration phase and initiating the expiration phase, and thereby dividing the breathing cycle time in a preselected ratio of inspiration time to expiration time; and a single ratio control means for selectively varying the ratio of inspiration time to expiration time independently of the breathing cycle time, said ratio control means including a movable piston separating said first and second chambers, whereby movement of said piston changes the ratio of inspiration time to expiration time independently of the breathing cycle time, by varying the ratio of the volumes of said first and second chambers independently of their total volume. 